Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, VA.
The Division of Immunology, Tulane National Primate Research Center, Covington, LA.
Brain Pathol. 2019 Nov;29(6):826-836. doi: 10.1111/bpa.12731. Epub 2019 May 14.
In the present study, we investigated whether colony-stimulating factor 1 receptor (CSF1R) is expressed on brain macrophages and microglia in the human and macaque brain and whether it is upregulated and activated after lentivirus infection in vivo and contributes to development of encephalitic lesions. We examined, using multi-label and semi-quantitative immunofluorescence microscopy, the protein expression level and cellular localization of CSF1R in brain tissues from uninfected controls and SIV-infected adult macaques with or without encephalitis and also from uninfected controls, HIV-infected encephalitic subjects and virally suppressed subjects. In the normal uninfected brain, CSF1R protein was detected only on microglia and brain macrophages but not on neurons, astrocytes or oligodendrocytes. Microglia constitutively expressed CSF1R at low levels, and its expression was largely unchanged in non-encephalitic and encephalitic animals. Brain macrophages, including perivascular macrophages (PVMs), expressed higher levels of CSF1R compared to microglia. Interestingly, we found significantly increased expression of CSF1R on the infected PVMs and lesional macrophages in the brains of encephalitic macaques. Moreover, the per cell expression of CSF1R determined by its mean pixel intensity (MPI) correlated positively with the MPI of SIV Gag p28 in SIV-infected PVMs. Using phosphorylated CSF1R at tyrosine residue 723 and phosphorylated signal transducer and activator of transcription 5 at tyrosine reside 694 as markers for CSF1R activation, we found selective activation of CSF1R signaling in infected brain macrophages in encephalitis. We also found colocalization of CSF1R and its ligand CSF1 in PVMs and lesional macrophages in the brains of encephalitic macaques and humans. Notably, elevated brain CSF1R expression was found in virally suppressed subjects. These findings point to opportunities for developing a specific approach targeting infected brain macrophages, with several brain-penetrant CSF1R inhibitors that are available now, in order to eliminate central nervous system macrophage reservoirs, while not affecting resting uninfected microglia and PVMs that show no CSF1R activation.
在本研究中，我们调查了集落刺激因子 1 受体（CSF1R）是否在人脑和猕猴脑中的脑巨噬细胞和小胶质细胞上表达，以及它是否在体内慢病毒感染后上调和激活，并导致脑炎病变的发展。我们使用多标记和半定量免疫荧光显微镜检查了未感染对照、感染 SIV 但无脑炎和无感染对照、HIV 感染脑炎患者和病毒抑制患者的脑组织中 CSF1R 的蛋白表达水平和细胞定位。在正常未感染的大脑中，仅在小胶质细胞和脑巨噬细胞上检测到 CSF1R 蛋白，但不在神经元、星形胶质细胞或少突胶质细胞上检测到。小胶质细胞低水平表达 CSF1R，在非脑炎和脑炎动物中其表达基本不变。脑巨噬细胞，包括血管周巨噬细胞（PVM），表达的 CSF1R 水平高于小胶质细胞。有趣的是，我们发现脑炎猕猴大脑中感染的 PVM 和病变巨噬细胞上 CSF1R 的表达显著增加。此外，通过其平均像素强度（MPI）确定的 CSF1R 细胞表达与其在感染的 PVM 中的 SIV Gag p28 的 MPI 呈正相关。使用 CSF1R 在酪氨酸残基 723 上的磷酸化和信号转导和转录激活因子 5 在酪氨酸残基 694 上的磷酸化作为 CSF1R 激活的标志物，我们发现 CSF1R 信号在脑炎中的感染脑巨噬细胞中选择性激活。我们还发现 CSF1R 和其配体 CSF1 在脑炎猕猴和人类大脑中的 PVM 和病变巨噬细胞中存在共定位。值得注意的是，在病毒抑制的患者中发现脑 CSF1R 表达升高。这些发现为开发针对感染的脑巨噬细胞的特定方法提供了机会，现在有几种可穿透大脑的 CSF1R 抑制剂可用于消除中枢神经系统巨噬细胞储库，而不会影响未感染的静止小胶质细胞和 PVM，它们没有 CSF1R 激活。
